1. Field of the Invention
The present invention relates to photoresist resins, photoresist compositions comprising the same, and processes for using the photoresist compositions. In particular, the present invention relates to photoresist resins comprising a mixture of polymers which have different properties, and methods for using the same.
2. Description of the Background Art
Resist flow processes are used in variety of industrial applications including production of semiconductor devices. Resist flow processes are often used in production of semiconductor devices to form a fine contact hole pattern. The resist flow process can be used to produce a contact hole pattern which exceeds the resolution of the exposing device. Typically, a resist flow process is used after a pattern is formed on a substrate using a photolithography process. The photolithography process generally involves an exposure process and a development process. The photolithography process forms a photoresist contact hole pattern having a maximum resolution equal to that of the exposing device. In the resist flow process, this initially formed pattern is then heated to a temperature higher than the glass transition temperature of the photoresist resin which causes the photoresist resin to flow. This flow of photoresist resin reduces the size of contact hole until a fine contact hole necessary for the integration process is obtained.
Thus, the resist flow process makes it possible to obtain contact holes smaller than the resolution of an exposing device. Unfortunately, the resist flow process can result in a sudden or excessive photoresist resin flow (i.e., xe2x80x9coverflowxe2x80x9d) which may result in a bent or collapsed contact hole pattern profile. This problem occurs typically at a temperature higher than the glass transition temperature of the photoresist resin.
The overflow can occur due to several factors including photoresist""s sensitivity to heat, imprecise temperature control, and imprecise control of the flow time. As shown in FIG. 1a, the flow rate of a photoresist composition containing a single photoresist resin increases rapidly as the temperature approaches 150xc2x0 C. As a result, the resulting contact hole pattern becomes bent and shrunken as shown in FIG. 1b. Without being bound by any theory, it is believed that this is due to the difference in flowable amount of the polymer present in the upper, center and lower portions of the contact hole pattern.
Attempts to solve the overflow problem by improving the baking process, such as maintaining a uniform baking temperature and/or controlling the precise baking time, have been mostly unsuccessful.
Accordingly, it is an object of the present invention to provide photoresist resins and photoresist compositions comprising the same which are useful in a resist flow process.
Another object of the present invention is to provide a resist flow process for forming a photoresist pattern using such photoresist composition.
Still another object of the present invention is to provide a contact hole formation method employing the photoresist pattern formed by the above-described process.